This invention relates principally to the railroad industry and specifically to the shunting of railroad cars.
As is well known to those skilled in the art, a railroad car such as a boxcar, flatcar, or the like, may spend as much or more time in a railroad facility being loaded, unloaded, or repaired, than it spends in actual use transporting goods between their point of origin and destination. During this time in the facility the railroad car must be moved about the yard either by itself or in combination with other similar cars in order to be loaded, unloaded, repaired, or stored until a fully marshalled series of railroad cars is ready to be assembled, connected to an engine and moved out. Since the vast majority of railroad cars are not individually powered, moving the cars about a yard, repair facility or loading warehouse, generally necessitates the use of some form of motorized device.
In major railroad yards where a great amount of such intra-yard movement is experienced, large shunt engines are used specifically for this purpose. In smaller facilities, however, where such movement is done less frequently, such as in an industrial yard or on a "spot-rip" track, the use of such a large shunt engine may be impractical either due to limited maneuvering space within the facility or due to the large expense involved in the purchase and maintenance of such a device. In such cases, various machines may be utilized to move railroad cars which machines have primary uses which differ substantially from the moving of railroad cars. Almost invariably these machines must be used in a mode for which they were not intended. As a result of such use, the safety factor, which may be within permissable limits for the primary use of the machine, may be reduced or eliminated. Under such circumstances, the danger to personnel and equipment is increased, in many cases, beyond reasonable limits.
Among such alternative methods which have been used is that of positioning a mobile loading crane, which is capable of movement alongside a railroad track, close to a railroad car, lowering the boom of the crane so that the bottom end is in contact with the side or the end of the boxcar, and driving the crane towards the desired destination, literally pushing the railroad car along the track. Such a method is inherently dangerous both because the boom end may slip from its contact with the car and also because, once in motion, the railroad car cannot be stopped by the crane. In order to stop the moving car, blocks or "chocks" must be maneuvered by other workers into the path of the car along the tracks at the desired stopping point.
It is also known to use a relatively small motorized device such as a forklift truck in combination with a cable, chain or the like in order to pull a boxcar to its desired destination in the yard. The use of this method, however, is limited both because of a stopping problem similar to that experienced in the use of the crane, and because a conventional forklift has always previously been found to be incapable of pulling more than one or two cars at a time. Finally, some mining operations use front end loaders to push the railroad cars in a manner similar to that used with the mobile cranes.
As is evidenced by the foregoing, it would be desirable to provide a safe method of shunting railroad cars under circumstances in which the use of a shunt engine is either impossible or impractical.
In addition, it would be desirable if such a method could be practiced with a device having other uses in that yard.
Finally, it would be desirable that such method and apparatus minimize or eliminate the possibility of personal injury or property damage resulting from their use.